I have a NSTextAttachment subclass with overridden attachmentBoundsForTextContainer:proposedLineFragment:glyphPosition:characterIndex: imageForBounds:textContainer:characterIndex:.
I need to redraw the attachment(s) at some point. Calling setNeedsDisplay on the UITextView doesn't work.
Any ideas? I'd like to avoid recreating attachments and/or the attributed string.
You'll want to use one of textView.layoutManager's methods.
invalidateDisplayCharacterRange:
imageForBounds:textContainer:characterIndex: will be called again.
attachmentBoundsForTextContainer:[...]Index: will not be called again.
Good if the image has been changed with another one of the same size.
invalidateLayoutForCharacterRange:actualCharacterRange:
imageForBounds:textContainer:characterIndex: will be called again.
attachmentBoundsForTextContainer:[...]Index: will be called again.
Good if the image has been changed with another one of a different size.
If you just want to update a single attachment, you may find this helper method I wrote helpful:
- (NSRange)rangeOfAttachment:(NSTextAttachment *)attachment {
__block NSRange ret;
[self.textStorage enumerateAttribute:NSAttachmentAttributeName
inRange:NSMakeRange(0, self.textStorage.length)
options:0
usingBlock:^(id value, NSRange range, BOOL *stop) {
if (attachment == value) {
ret = range;
*stop = YES;
}
}];
return ret;
}
You can pass the resulting NSRange of this method to the first argument of either of those invalidate methods. For the actualCharacterRange: argument of the second method, I've been passing in NULL without any problems.
Well, after some digging, that can done by invalidating the layout manager:
[textView.layoutManager invalidate....]
Apple docs
If you just want to change the NSTextAttachment which is init by a image, I suggest you to use
setAttachmentSize:size forGlyphRange:range
Related
My app pulls HTML from an API, converts it into a NSAttributedString (in order to allow for tappable links) and writes it to a row in an AutoLayout table. Trouble is, any time I invoke this type of cell, the height is miscalculated and the content is cut off. I have tried different implementations of row height calculations, none of which work correctly.
How can I accurately, and dynamically, calculate the height of one of these rows, while still maintaining the ability to tap HTML links?
Example of undesired behavior
My code is below.
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
switch(indexPath.section) {
...
case kContent:
{
FlexibleTextViewTableViewCell* cell = (FlexibleTextViewTableViewCell*)[TableFactory getCellForIdentifier:#"content" cellClass:FlexibleTextViewTableViewCell.class forTable:tableView withStyle:UITableViewCellStyleDefault];
[self configureContentCellForIndexPath:cell atIndexPath:indexPath];
[cell.contentView setNeedsLayout];
[cell.contentView layoutIfNeeded];
cell.selectionStyle = UITableViewCellSelectionStyleNone;
cell.desc.font = [UIFont fontWithName:[StringFactory defaultFontType] size:14.0f];
return cell;
}
...
default:
return nil;
}
}
- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath {
UIFont *contentFont = [UIFont fontWithName:[StringFactory defaultFontType] size:14.0f];
switch(indexPath.section) {
...
case kContent:
return [self textViewHeightForAttributedText:[self convertHTMLtoAttributedString:myHTMLString] andFont:contentFont andWidth:self.tappableCell.width];
break;
...
default:
return 0.0f;
}
}
-(NSAttributedString*) convertHTMLtoAttributedString: (NSString *) html {
return [[NSAttributedString alloc] initWithData:[html dataUsingEncoding:NSUTF8StringEncoding]
options:#{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType,
NSCharacterEncodingDocumentAttribute: #(NSUTF8StringEncoding)}
documentAttributes:nil
error:nil];
}
- (CGFloat)textViewHeightForAttributedText:(NSAttributedString*)text andFont:(UIFont *)font andWidth:(CGFloat)width {
NSMutableAttributedString *mutableText = [[NSMutableAttributedString alloc] initWithAttributedString:text];
[mutableText addAttribute:NSFontAttributeName value:font range:NSMakeRange(0, text.length)];
UITextView *calculationView = [[UITextView alloc] init];
[calculationView setAttributedText:mutableText];
CGSize size = [self text:mutableText.string sizeWithFont:font constrainedToSize:CGSizeMake(width,FLT_MAX)];
CGSize sizeThatFits = [calculationView sizeThatFits:CGSizeMake(width, FLT_MAX)];
return sizeThatFits.height;
}
In the app I'm working on, the app pulls terrible HTML strings from a lousy API written by other people and converts HTML strings to NSAttributedString objects. I have no choice but to use this lousy API. Very sad. Anyone who has to parse terrible HTML string knows my pain. I use Text Kit. Here is how:
parse html string to get DOM object. I use libxml with a light wrapper, hpple. This combination is super fast and easy to use. Strongly recommended.
traverse the DOM object recursively to construct NSAttributedString object, use custom attribute to mark links, use NSTextAttachment to mark images. I call it rich text.
create or reuse primary Text Kit objects. i.e. NSLayoutManager, NSTextStorage, NSTextContainer. Hook them up after allocation.
layout process
Pass the rich text constructed in step 2 to the NSTextStorage object in step 3. with [NSTextStorage setAttributedString:]
use method [NSLayoutManager ensureLayoutForTextContainer:] to force layout to happen
calculate the frame needed to draw the rich text with method [NSLayoutManager usedRectForTextContainer:]. Add padding or margin if needed.
rendering process
return the height calculated in step 5 in [tableView: heightForRowAtIndexPath:]
draw the rich text in step 2 with [NSLayoutManager drawGlyphsForGlyphRange:atPoint:]. I use off-screen drawing technique here so the result is an UIImage object.
use an UIImageView to render the final result image. Or pass the result image object to the contents property of layer property of contentView property of UITableViewCell object in [tableView:cellForRowAtIndexPath:].
event handling
capture touch event. I use a tap gesture recognizer attached with the table view.
get the location of touch event. Use this location to check if user tapped a link or an image with [NSLayoutManager glyphIndexForPoint:inTextContainer:fractionOfDistanceThroughGlyph] and [NSAttributedString attribute:atIndex:effectiveRange:].
Event handling code snippet:
CGPoint location = [tap locationInView:self.tableView];
// tap is a tap gesture recognizer
NSIndexPath *indexPath = [self.tableView indexPathForRowAtPoint:location];
if (!indexPath) {
return;
}
CustomDataModel *post = [self getPostWithIndexPath:indexPath];
// CustomDataModel is a subclass of NSObject class.
UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:indexPath];
location = [tap locationInView:cell.contentView];
// the rich text is drawn into a bitmap context and rendered with
// cell.contentView.layer.contents
// The `Text Kit` objects can be accessed with the model object.
NSUInteger index = [post.layoutManager
glyphIndexForPoint:location
inTextContainer:post.textContainer
fractionOfDistanceThroughGlyph:NULL];
CustomLinkAttribute *link = [post.content.richText
attribute:CustomLinkAttributeName
atIndex:index
effectiveRange:NULL];
// CustomLinkAttributeName is a string constant defined in other file
// CustomLinkAttribute is a subclass of NSObject class. The instance of
// this class contains information of a link
if (link) {
// handle tap on link
}
// same technique can be used to handle tap on image
This approach is much faster and more customizable than [NSAttributedString initWithData:options:documentAttributes:error:] when rendering same html string. Even without profiling I can tell the Text Kit approach is faster. It's very fast and satisfying even though I have to parse html and construct attributed string myself. The NSDocumentTypeDocumentAttribute approach is too slow thus is not acceptable. With Text Kit, I can also create complex layout like text block with variable indentation, border, any-depth nested text block, etc. But it does need to write more code to construct NSAttributedString and to control layout process. I don't know how to calculate the bounding rect of an attributed string created with NSDocumentTypeDocumentAttribute. I believe attributed strings created with NSDocumentTypeDocumentAttribute are handled by Web Kit instead of Text Kit. Thus is not meant for variable height table view cells.
EDIT:
If you must use NSDocumentTypeDocumentAttribute, I think you have to figure out how the layout process happens. Maybe you can set some breakpoints to see what object is responsible for layout process. Then maybe you can query that object or use another approach to simulate the layout process to get the layout information. Some people use an ad-hoc cell or a UITextView object to calculate height which I think is not a good solution. Because in this way, the app has to layout the same chunk of text at least twice. Whether you know or not, somewhere in your app, some object has to layout the text just so you can get information of layout like bounding rect. Since you mentioned NSAttributedString class, the best solution is Text Kit after iOS 7. Or Core Text if your app is targeted on earlier iOS version.
I strongly recommend Text Kit because in this way, for every html string pulled from API, the layout process only happens once and layout information like bounding rect and positions of every glyph are cached by NSLayoutManager object. As long as the Text Kit objects are kept, you can always reuse them. This is extremely efficient when using table view to render arbitrary length text because text are laid out only once and drawn every time a cell is needed to display. I also recommend use Text Kit without UITextView as the official apple docs suggested. Because one must cache every UITextView if he wants to reuse the Text Kit objects attached with that UITextView. Attach Text Kit objects to model objects like I do and only update NSTextStorage and force NSLayoutManager to layout when a new html string is pulled from API. If the number of rows of table view is fixed, one can also use a fixed list of placeholder model objects to avoid repeat allocation and configuration. And because drawRect: causes Core Animation to create useless backing bitmap which must be avoided, do not use UIView and drawRect:. Either use CALayer drawing technique or draw text into a bitmap context. I use the latter approach because that can be done in a background thread with GCD, thus the main thread is free to respond to user's operation. The result in my app is really satisfying, it's fast, the typesetting is nice, the scrolling of table view is very smooth (60 fps) since all the drawing process are done in background threads with GCD. Every app needs to draw some text with table view should use Text Kit.
You need to update intrinsic content size.
I assume that you set attributed text to label in this code [self configureContentCellForIndexPath:cell atIndexPath:indexPath];
So, it should look like this
cell.youLabel.attributedText = NSAttributedString(...)
cell.youLabel.invalidateIntrinsicContentSize()
cell.youLabel.layoutIfNeeded()
You height calculation code (CGFloat)textViewHeightForAttributedText:(NSAttributedString*)text andFont:(UIFont *)font andWidth:(CGFloat)width should be replaced with cell height calculation using prototyping cell.
I'm assuming you are using a UILabel to display the string?
If you are, I have had countless issues with multiline labels with autoLayout. I provided an answer here
Table View Cell AutoLayout in iOS8
which also references another answer of mine that has a breakdown of how i've solved all my issues. Similar issues have cropped up again in iOS 8 that require a similar fix in a different area.
All comes down to the idea of setting the UILabel's preferredMaxLayoutWidth every time is bounds change. What also helped is setting the cells width to be the width of the tableview before running:
CGSize size = [cell.contentView systemLayoutSizeFittingSize:UILayoutFittingCompressedSize];
I ran into a very similar issue on another project where fields using NSAttributedString weren't rendering with the correct height. Unfortunately, there are two bugs with it that made us completely drop using it in our project.
The first is a bug that you've noticed here, where some HTML will cause an incorrect size calculation. This is usually from the space between the p tags. Injecting CSS sort of solved the issue, but we had no control over the incoming format. This behaves differently between iOS7 and iOS8 where it's wrong on one and right on the other.
The second (and more serious) bug is that NSAttributedString is absurdly slow in iOS 8. I outlined it here: NSAttributedString performance is worse under iOS 8
Rather than making a bunch of hacks to have everything perform as we wanted, the suggestion of using https://github.com/Cocoanetics/DTCoreText worked out really well for the project.
If you can target iOS 8 using dynamic cell sizing is the ideal solution to your problem.
To use dynamic cell sizing, delete heightForRowAtIndexPath: and set self.tableView.rowHeight to UITableViewAutomaticDimension.
Here is a video with more details:
https://developer.apple.com/videos/wwdc/2014/?include=226#226
You can replace this method to calculate the height of attributed string:
- (CGFloat)textViewHeightForAttributedText:(NSAttributedString*)text andFont:(UIFont *)font andWidth:(CGFloat)width {
CGFloat result = font.pointSize + 4;
if (text)
result = (ceilf(CGRectGetHeight([text boundingRectWithSize:CGSizeMake(width, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading context:nil])) + 1);
return result;
}
Maybe the font you changed doesnt matches with the font of content on html pages. So, use this method to create attributed string with appropriate font:
// HTML -> NSAttributedString
-(NSAttributedString*) convertHTMLtoAttributedString: (NSString *) html {
NSError *error;
NSDictionary *options = #{NSDocumentTypeDocumentAttribute: NSHTMLTextDocumentType};
NSAttributedString *attrString = [[NSAttributedString alloc] initWithData:[html dataUsingEncoding:NSUTF8StringEncoding] options:options documentAttributes:nil error:&error];
if(!attrString) {
NSLog(#"creating attributed string from HTML failed: %#", error.debugDescription);
}
return attrString;
}
// force font thrugh & css
- (NSAttributedString *)attributedStringFromHTML:(NSString *)html withFont:(UIFont *)font {
return [self convertHTMLtoAttributedString:[NSString stringWithFormat:#"<span style=\"font-family: %#; font-size: %f\";>%#</span>", font.fontName, font.pointSize, html]];
}
and in your tableView:heightForRowAtIndexPath: replace it with this:
case kContent:
return [self textViewHeightForAttributedText:[self attributedStringFromHTML:myHTMLString withFont:contentFont] andFont:contentFont andWidth:self.tappableCell.width];
break;
You should be able to convert to an NSString to calculate the height like this.
-(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{
UIFont * font = [UIFont systemFontOfSize:15.0f];
NSString *text = [getYourAttributedTextArray objectAtIndex:indexPath.row] string];
CGFloat height = [text boundingRectWithSize:CGSizeMake(self.tableView.frame.size.width, maxHeight) options:(NSStringDrawingUsesLineFragmentOrigin|NSStringDrawingUsesFontLeading) attributes:#{NSFontAttributeName: font} context:nil].size.height;
return height + additionalHeightBuffer;
}
[cell.descriptionLabel setPreferredMaxLayoutWidth:375.0];
I want my app to be when you click the stepper it will resize the font in a UITextView. The problem is I'm getting errors.
- (IBAction)myStepper:(id)sender {
[myStepper setMinimumValue:14.0]
self.myStepper.maximumValue =20.0;
UIFont newSize = [myTextView fontWithSize:self.stepper.value];
self.myTextView.font = newSize;
}
This all of my code, am I missing something?
You are missing a self and a semicolon in the first line:
[self.myStepper setMinimumValue:14.0];
And an asterisk and self in this line, and stepper should be myStepper:
UIFont *newSize = [self.myTextView fontWithSize:self.myStepper.value];
I would clean your method a bit like this:
- (IBAction)myStepperValueChanged:(UIStepper *)sender {
[sender setMinimumValue:14.0];
[sender setMaximumValue:20.0];
UIFont * newSize = [UIFont fontWithName:myTextView.font.fontName size:sender.value];
[self.myTextView setFont:newSize];
}
but I'd put the first two lines into the -viewDidLoad method as part of the standard init procedure, if they are static values in runtime using the outlet's name (I assume it is myStepper in your class):
[myStepper setMinimumValue:14.0];
[myStepper setMaximumValue:20.0];
or I'd set these values in the Interface Builder, and you'd not need to deal with any outlet for your stepper at all.
NOTE: it is hard to tell which solution would fit better for you, you have not shared too much information which could help me to recommend a specific solution.
For easier code-reading, you shouldn't give your action method the same name of your UISteppert property. Change it to -(IBAction)stepperValueChanged:(id)sender for example.
You don't need to set the min and max value in this method, but in your initialization methods
- (void) viewDidLoad
{
[super viewDidLoad];
// Various implementation
self.myStepper.minimumValue = 14;
self.myStepper.maximumValue = 20.0;
}
- (IBAction) stepperValueChanged:(id)sender
{
self.myTextView.font = [UIFont fontWithSize:self.myStepper.value];
}
It looks like you are some issues understanting the differences between method and properties, you should read some documentation and tutorials if you're beginning development (and welcome to the development world ;) ).
EDIT :
The property myStepper doesn't exists in your class. If you use interface builder, you have to link your stepper to an UIStepper property : this apple tutorial will help you : https://developer.apple.com/library/ios/recipes/xcode_help-interface_builder/articles-connections_bindings/CreatingOutlet.html .
Otherwise, if you don't use Interface Builder, you must add an UIStepper property to your class and allocate it by yourself.
I have an NSAttributedString that is reporting a boundingRectWithSize (and by extension a UITextView which improperly calculates its sizeThatFits) when the font size is decreased from the font size that was used to create it.
It doesn't happen on all NSAttributedStrings for which I do similar operations, so here's the steps to reproduce.
Use a non-standard font that does not include the full unicode character set.
Make sure the string includes characters in this "unsupported" set. iOS will render them as Helvetica in the proper size.
Scale your font down on all font attributes in your NSAttributedString. My code for doing so that produced the issue looks like this.
From inside a UITextView subclass:
NSMutableAttributedString *mutableString = [self.attributedText mutableCopy];
[mutableString enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, mutableString.length) options:0 usingBlock:^(id value, NSRange range, BOOL *stop) {
if (value) {
UIFont *oldFont = (UIFont *)value;
UIFont *newFont = [oldFont fontWithSize:oldFont.pointSize - 1];
[mutableString removeAttribute:NSFontAttributeName range:range];
[mutableString addAttribute:NSFontAttributeName value:newFont range:range];
}
}];
self.attributedText = [mutableString copy];
I noticed that while running this code in a while loop checking sizeThatFits to know when the text is small enough to fit that I would have a race to zero occur in some circumstances. The height is being calculated as 60px for any font value smaller than what I started with, which happens to be 50px.
When NSLoging the NSAttributedString I find that there are several attributes that I did not add with the key NSOriginalFont which does not appear to be in the list of supported attributes here. What's going on with NSOriginalFont? Why is my size being calculated incorrectly?
I ended up fixing this but found a lack of information on the web about it, so I decided to document my solution here.
NSOriginalFont attributes are created when the font used doesn't support one or more characters in the string. NSAttributedString adds these attributes that track what the font was "supposed" to be before a substitution to Helvetica occurred. I could make up a situation where this is useful (an all-caps font that you sometimes run uppercaseString: on?) but it wasn't useful to me.
In fact it was harmful. As I iterated through my font related attributes to decrease the size as shown above the visible size of the text was decreasing but the NSOriginalFont attribute retained a reference to the large size.
There's no built in constant for NSOriginalFont but if you call it by name it's possible to strip it from your NSMutableAttributedString. If you do you'll begin to get proper results from sizeThatFits, boundingRectWithSize, and other similar functions assuming that you're passing the correct options.
I ended up creating a simple category method on NSMutableAttributedString, included below, that works well.
NSMutableAttributedString+StripOriginalFont.h
#interface NSMutableAttributedString (StripOriginalFont)
- (void) stripOriginalFont;
#end
NSMutableAttributedString+StripOriginalFont.m
#implementation NSMutableAttributedString (StripOriginalFont)
- (void) stripOriginalFont{
[self enumerateAttribute:#"NSOriginalFont" inRange:NSMakeRange(0, self.length) options:0 usingBlock:^(id value, NSRange range, BOOL *stop) {
if (value){
[self removeAttribute:#"NSOriginalFont" range:range];
}
}];
}
#end
Presumably you could simply modify it to keep it "in-sync" instead of removing it entirely but it wasn't useful to me for this particular project.
For stripping in swift you can use this extension:
extension NSAttributedString {
func strippedOriginalFont() -> NSAttributedString? {
let mutableCopy = self.mutableCopy() as? NSMutableAttributedString
mutableCopy?.removeAttribute(NSAttributedStringKey(rawValue: "NSOriginalFont"), range: NSMakeRange(0, self.length))
return mutableCopy?.copy() as? NSAttributedString
}
}
Don't know if this will help solve your issue, but check out my solution for auto-sizing text UITextView here: https://stackoverflow.com/a/30400391/1664123
Create NSTextStorage object and init with the attributedString.
and calculate bounds.
NSTextStorage *attributedText = [[NSTextStorage alloc] initWithAttributedString:[[NSAttributedString alloc] initWithString:text attributes:#{NSFontAttributeName:systemFont}]];
CGRect textRect = [attributedText boundingRectWithSize:CGSizeMake(textW, CGFLOAT_MAX) options:NSStringDrawingUsesLineFragmentOrigin context:nil];
I had the same problem. when I call textView.setAttributedString(), it will automatically add NSOriginalFont attribute for me which lead to the wrong size. I also use sizeThatFits to calculate height.
The reason we got the wrong size is textView use the NSOriginalFont to calculate size which is not suitable for changed NSFont.
But if we use a NSTextStorage to create the attributedString and call textView.setAttributedText, then it will not add NSOriginalFont(I don't know why, but this fixes my problem) and the calculation of size will get the right answer.
Simple Code:
func getAttributedStringForTextView(content: String) -> NSAttributedString {
var attriString = NSMutableAttributedString(string: content)
// add attributes here
...
// at last, use an NSTextStorage to wrap the result
return NSTextStorage(attributedString: attriString)
}
Hope this helps.
So in my code, I was checking if my characters fit in my Label or not and had the following line :
return self.adjustsLetterSpacingToFitWidth;
This was placed in an implementation of UILabel. Can someone tell me just what is the exact alternative for this? The documentation says - Use NSKernAttributeName, but I wasn't quite able to understand that. Can someone help me on this?
In the larger sense - The method is called as:
xLab.adjustLetterSpacingToFitWidth = YES;
In my code, I have:
#implementation UILabel ()
- (BOOL) getter {
return self.adjustsLetterSpacingToFitWidth;
}
- (void) setter:(BOOL) setVal {
self.adjustsLetterSpacingToFitWidth = setVal;
}
#end
First of all, your getter and setter are entirely superfluous as shown; wherever you call getter and/or setter, you could simply get/set adjustsLetterSpacingToFitWidth directly.
As for the question of how to do auto-kerning with NSKernAttributeName, Apple's documentation says: “To turn on auto-kerning in the label, set NSKernAttributeName of the string to [NSNull null]”, i.e., you would do something like:
NSMutableAttributedString *s;
s = [[NSMutableAttributedString alloc] initWithString:my_uilabel.text];
[s addAttribute:NSKernAttributeName
value:[NSNull null]
range:NSMakeRange(0, s.length)];
my_uilabel.attributedText = s;
But if you did not want to do automatic adjustment of letter spacing but rather find out whether the text fits in the label or not, you might want to check the various methods in NSString UIKit additions. (This guess of intent is based on the wording in the original question.)
Is anyone using this delegate method ? I get callbacks on
- (BOOL)textViewShouldBeginEditing:(UITextView *)textView
But not on this one. The documentation seems a bit ambiguous about what this is intended for
- (BOOL)textView:(UITextView *)textView shouldInteractWithTextAttachment:(NSTextAttachment *)textAttachment inRange:(NSRange)characterRange
According to the documentation on the Web this is what its intended for:
Discussion
The text view calls this method if the user taps or long-presses the text attachment and its image property is not nil. Implementation of this method is optional. You can use this method to trigger an action in addition to displaying the text attachment inline with the text.
And here is Xcode 5 documentation:
Asks the delegate if the specified text view should display the provided text attachment in the given range of text.
The text view calls this method when a text attachment character is recognized in its text container by a data detector. Implementation of this method is optional. You can use this method to trigger an alternative action besides displaying the text attachment inline with the text in the given range.
EDIT:
Mmm OK I figured out the problem. If I paste an image in from iOS then it works, however if the image was pasted in from OS X it does not. It seems that the actual attachment formats used are not quite the same on both platforms despite the fact that the image appears to show up correctly in the text views. On closer inspection the NSTextAttachment classes don't appear to be the same on iOS as on OS X.
If anyone can shed any light on the cross platform compatibility here please do.
Also if I save the attributed string after pasting the image in on iOS and then retrieve it and display it in the UITextView interaction with the attachment is no longer possible. It would appear that when storing the image the image is actually placed in contents if contents is nil. So maybe I am going to have to iterate through all attachments to check what data is stored where particularly to figure out any differences in behaviour across the OS X and iOS platforms.
FURTHER EDIT:
The method only gets called if the attachment image is NOT nil and despite the fact that an image is displayed the actual image attribute can actually be nil, silly me! Anyway the fix seems to be to check all the attachments in the attributed string and to set their image attribute to something, usually the contents of the fileWrapper. The default NSTextAttachment behaviour seems to be to store the image in the fileWrapper when its archived but it does not do the reverse when its unarchived. Anyway I want to retain the original image in the attachment but depending on the device display a suitably scaled version of the original !
The chief thing is that the text view's editable property must be NO and it's selectable property must be YES. Those are the only circumstances under which this delegate method is called. If you are getting shouldBeginEditing then your text field is editable which is exactly what it must not be.
Here is what I do to ensure the NSTextAttachments image attribute gets set when restoring the UITextView's attributed string from archived data (in this case whenever the user selects a record from a Core Data store).
I set the UITextView up as a delegate for textStorage and in the didProcessEditing look for any attachments that may have been added and then check that their image attribute is set. I am also setting the scaling factor on the image to make sure the image scales appropriately for the device.
This way I don't loose the original resolution of the image and if the user wants to view it in more detail I provide the option to open it in an image browser window from a popup menu.
Hope this helps someone else.
EDIT:
Check here for more details on NSTextView and UITextView http://ossh.com.au/design-and-technology/software-development/
- (void)textStorage:(NSTextStorage *)textStorage didProcessEditing:(NSTextStorageEditActions)editedMask range:(NSRange)editedRange changeInLength:(NSInteger)delta {
//FLOG(#"textStorage:didProcessEditing:range:changeInLength: called");
[textStorage enumerateAttributesInRange:editedRange options:NSAttributedStringEnumerationLongestEffectiveRangeNotRequired usingBlock:
^(NSDictionary *attributes, NSRange range, BOOL *stop) {
// Iterate over each attribute and look for a Font Size
[attributes enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
if ([[key description] isEqualToString:NSAttachmentAttributeName]) {
NSTextAttachment *attachment = obj;
//Reset the image attribute and scale for the device size if necessary
[self resetAttachmentImage:attachment];
}
}];
}];
}
- (void)resetAttachmentImage:(NSTextAttachment*)attachment {
UIImage *image = [attachment image];
float factor = 2;
if (image == nil) {
if (attachment.fileWrapper == nil || !attachment.fileWrapper.isRegularFile) {
attachment.image = [UIImage imageNamed:#"unknown_attachment.png"];
return;
}
//Usually retrieved from store
image = [UIImage imageWithData:attachment.fileWrapper.regularFileContents];
} else {
// Convert any pasted image
image = [UIImage imageWithData:UIImagePNGRepresentation(image)];
}
float imgWidth = image.size.width;
// If its wider than the view scale it to fit
if (imgWidth > _viewWidth) {
factor = imgWidth / _viewWidth + 0.5;
attachment.image = [UIImage imageWithData:UIImagePNGRepresentation(image) scale:factor];
} else {
attachment.image = [UIImage imageWithData:UIImagePNGRepresentation(image) scale:_scale];
}
}